Astronomers Make an Accidental Discovery: Tiny Dwarf Galaxy Bedin 1

One of the amazing things about scientific research is that we don’t only learn about the things we’re looking at — sometimes we make amazing discoveries by chance as well. That’s what happened this week, when astronomers accidentally discovered a new galaxy while studying part of the Milky Way.

Astronomers were using data from the Hubble Space Telescope to study white dwarf stars in the globular cluster NGC 6752, a spherical group of stars that orbit around the core of the Milky Way. They were hoping to learn about how old the globular cluster is by studying these stars, but in the process they found something unexpected. When looking at an area right on the edge of the field of view of Hubble’s Advanced Camera for Surveys, they spotted a clump of faint stars. But on further inspection of their brightness and temperatures, the scientists realized that these stars were not a part of the globular cluster and were in fact much, much more distant.

The newly observed stars were in fact millions of light-years away and are part of a relatively small galaxy that is just 3000 light-years across. The galaxy is not only tiny but is also very faint, meaning that it is unlikely we would have ever discovered it had astronomers not been studying the area in front of the galaxy in detail. The new galaxy is classified as a dwarf spheroidal galaxy and has been named Bedin 1 after Luigi Bedin, an astronomer at the Italian National Institute for Astrophysics (INAF) and the leader of the team who made the discovery.

This image, taken with the NASA/ESA Hubble Space Telescope, shows a part of the globular cluster NGC 6752. The observations were made to study white dwarfs within it and to use these stars to measure the age of the globular cluster. Analyzing the data, astronomers discovered a previously unknown galaxy behind the globular cluster. The galaxy, nicknamed Bedin 1, is visible as a collection of faint stars at the top left of the image. ESA/Hubble, NASA, Bedin et al.

Bedin 1 is an unusual galaxy in that it is very isolated from others, lying 30 million light-years from the Milky Way and 2 million light-years from the nearest large galaxy, NGC 6744. This makes it likely the most isolated small dwarf galaxy discovered so far.

To get an impression of how Bedin 1 was discovered, the below video shows a zoomed in journey to globular cluster NGC 6752, with a final view captured by the Hubble of the bright stars of the cluster in the foreground and faint stars of a background galaxy behind. This background galaxy is Bedin 1, the galaxy that was found by accident.